NO. 1331. 



DRAGON-FLY WING VENATION— NEEBH AM. 



715 



upward arching of the medial branches reaches its climax in some 

 Calopterytrina% when JI/1+2 after separating from J/., again rejoins the 

 radius; its basal part tlien appears as a cross vein, and when its trunk 

 again frees itself it appears as a branch of the radius. Pseudophaea 

 (Plate Lll, iig. 8), Calopteri/.r (tig. 34), and VMaJIs (tig. 41) have pre- 

 served the steps by which such condition has been attained. 



In Epigomjykus (tig. 8) there is a curious tendency for these medial 

 branches to become conjoined just after their separate (h^partun^ fi-oni 

 the arculus. 



In all these tendencies cuticularisation outruns tracheation; the 

 veins become sharply angulated; the trachea^ much less so. This will 

 be clearly seen by comparing nymphal (Plate XXXII, tigs. 2 and ?>) 

 and adult (Plate XXXV, tig. 3) wings of Lantlnis j^arvuUi^. 



FiQ. 8.— Wings of Epigomphus paludosus Selys. 



The triangle has been called by several writers the "cardinal cell," 

 and worthily, for it is a feature of cardinal importance in tlie Odonate 

 wing." ^Ve have already observed that it is ordinarily fornunl in 

 Gomphux and others of the suborder Anisoptera, between an oblique 

 deflected portion of the cu])itus and two cross veins approximated 

 upon the hindmost branch of the media. Between the proximal one 

 of these two cross veins and the arculus is a narrow space which may 

 conveniently be termed the '"supertriaiigle" (.v., of all the tigures; 

 also called elsewhere "supnitriangular space"). 



The quadrangle of the Zygoptera.— In the suborder Zygoptera tri- 

 angle and supertriangle l)ear different relations to each other and to 

 surrounding parts of the wing. Together they constitute a unit of 

 wing structure. They are placed in line, not directed apart by an 



« It is not always triangular, but the exceptions are few. The name is a very con- 

 venient one and in general use, and I use it in a strictly technical sense without 

 regard to shape. 



